Equalizing brake for vehicles



Aug.16,1927. 1,639,320 s. K. WELLMAN ET AL EQUALIZING BRAKE FOR VEHICLES Fil ed Dec. 7. i923 INVENTORS Patented Aug. 16, 1927.

if UNITED STATES PATENT OFFICE.

SAMUEL K. WELLMAN'AN D GORDON B. PENNINGTON, OF CLEVELAND HEIGHTS, OHIO.

EQUALIZING BRAKE FOR VEHICLES.

Application filed December 7, 1923. Serial No. 879,207.

The invention relates to im rovements in vehicle brake mechanisms whic are designed to operate on two or more wheels of-the vehicle.

6 The ob'ect of our invention is to provide more per ect equalization of the brakin effort applied to two or more vehicle -w eels and consists in an equalizing mechan sm which is actuated directly by the braking l torques on the separate wheels.

Heretofore, it has been the general practice to attempt to secure equalization of the braking efforts on several wheels by equallzing the normal pressures a plied ,to the braking surfaces. As the coe cients of friction of the latter surfaces fre uently, however, vary through a range of rom .2 to .5, the resultant braking eiforts will vary in the same proportion.

This latter variation can be reduced to a negligible quantity by mechanism which operates to directly equalize the braking torques. Our invention consists in a simple and practical device for this urpose.

' Referring to the attached rawings, Figure 1 shows a preferred form of our invention applied to the rear axle of an automobile, viewed from the rear of the latter, and partially cutaway.

the section being taken on the line 2-2 in Figure 1.

Fi re 3 is an enlarged sectional view of the uid reservoir.

Referring in detail to the mechanism illustrated, 1 indicates an axle of usual construction carryin the wheels 2 to which are fixed the brake rums 3.

Brackets 4 are fixed to lugs 1 of the axle 4 1 by rivets 5. Cylinders 4 are formed integral with brackets 4. Pistons 7 fixed to piston rods 8 are mounted in cylinders 4 with substantially liquid-tight fits. Cylinder heads 9 are provided with holes 9 to permit the passage of and to ide piston rods 8. Springs 10 are placed etween pistons 7 and the tops of the cylinders 4*. Passages 4" are formed in the walls of-cylinders 4 Pipes 11 are held in connection with passages 4", and likewise in connection. with passages 18 of the fluid reservoir 18 by the union nuts 12. The reservoir 18 may be carried at any convenient point and in any convenient manner.

6 The cylinders 4 above the istons 7 and the pipes 11' and the 'oil reservoir 18 are filled Figure 2 is a sectional view of the axle,

with an liquid 19 upon the surface of which floats t e piston 20 carrying the proiection 20. The reservoir cover 21 which is t read-- ed into the reservoir 18 is formed with a passage 21 which loosely fits the projection 20 of the piston 20. The catch 22 is held in engagement by the spring 23 with notches 20 on the projection 20' which are so cut as to permit free downward movement of the latter. An air dome 20 is formed inside the piston 20.

v The braking material 24 is fixedby means of rivets 16 to the brake carrying bands 14. The two ends of the brake carrying bands 14 are fixed to end pieces 25 which are pivotally fixed to the levers 26 by means of the pins 27. Brake rods 28 are pivoted to the levers 26 by means of pins 29. Lugs 15 are fixed to the brake carrying bands 14 by means of rivets 13and normally rest upon projections 4 of brackets 4 The manner of operatidn is" as follows: When the brake rods 28 arepulled through any convenient arrangement of levers, which willcause both rods to be moved thru substantially the same distance, the brake carrying bands 14 are caused to contract and press the braking material 24 against the brake drums 3. The rotation of the latter, which is in the direction of the arrow when the vehicle is going forward, develops thru friction a force tending to rotate the braking material 24 and the brake carrying bands 14 in the same direction. This force is applied thru the ln 15 to the piston rods 8 and through the atter to the pistons 7 and to the springs 10 and the liquid 19. As the springs 10 are purposely given a very insuflicient initial compression to resist the a plied forces the pistons 7 move, causing t e liquid to flow from each side into the reservoir 18. As the piston 20 is given a substantially liquid tight fit in the reservoir 18 and as this piston is prevented from moving upwards by the catch 22, the only space for the enterin liquid to flow into is the air dome 20, w ich it does, compressing the air in the latter until a sufiicient pressure is developed to counterbalance the braking forces on the pistons 7. When the pull .on the brake rods 28 is relieved the braking forces va'nish and the pressure of the air- ,in the air dome 20, aided by the springs 10,

replace the elements of the mechanism in their original relation.

It will be evident that the rotation of the brake carryin bands 14, described, is in such a direction, w en the vehicle 1s moving forward, as to ofiset the ori inal pull on the brake rods 28 and to diminish the contraction of the braking material and thereby to diminish the braking force.

Furthermore, it will be evident that the resisting forces due to the pressure of the liquid 19 on the pistons 7 must at all times be equal except for a negligible variation due to pipe resistance and therefore, as the springs 10 are purposely made relatively weak, the total resisting forces on the pistons 7 will at all times be substantially equal.

If then variations of coefficients of frlc tion or of dimensions of parts cause initially a greater brakin force to be developed, for example, on the Ieft brake drum than on the right, the left brake carrying band will be rotated thru a greater angle than the right until by such rotation the pull on the left brake rod is sufliciently decreased to equallze the braking torques after which the system will be in equilibrium.

When the vehicle is moving backward the rotation of the brake carryin bands is resisted directly by the projections 4 of the brackets 4 and no equalization occurs.

We prefer to compensate for any leakage whichimay occur, by the downward movement of the piston 20, which is made of the proper specific gravity and form to float on the surface of the liquid, and which is fitted to the reservoir with a clearance just suflicient to allow the passage of the liquid at a sufiicient rate to compensate for leakage but not suflicient to cause any appreciable loss of liquid during the brief interval during which the brakes are applied. It will be understood, however, that such compensation for leakage is incidental and not an essential part of our invention.

It will be evident that our invention may be applied to equalize the braking on any number of wheels in the same manner as, in the application herein described, to two wheels. Also that it is not limited to any specific manner of applying the brakes as this maybe thru any mechanical or h draulic means. Nor is it limited to the spef cific equalizing means shown as this may be greatly varied in construction provided the' brake carrying members are prevented from rotating with the wheels by elements of the equalizing mechanism.

We claim:

1. In combination' a pluralit members, brakes adapted to h of rotatable ear on said into contact with said members, brake carrying elements receiving the frictional forces resulting from said contact, and hydraulic means connected to said brake carrying elemembers, mechanism for forcing said brakesments and operated by the said frictional forces to equalize the latter forces.

2. In a vehicle, the combination of a plurality of wheels, brake drums fixed to said wheels, brakes adapted to bear on said brake drums, mechanism for forcing said brakes into contact with said brake drums, and hydraulic means for varying the force of said contact on the various drums toequalize the resulting frictional torques on the latter.

3. In a vehicle, the combination of a plurality of wheels, brake drums fixed to said wheels, brakes adapted to bear on said brake drums, mechanism for forcing said brakes into contact with said brake drums, brake carrying elements receivin the frictional torques resulting from sai contact, fluid equalizing means connected to said brake carrying elements so disposed as to resist and be operated by said frictional torques to equalize the latter when the vehicle is going in one'direction and. stops fixed to' non-rotating portions of the vehicle so disposed as to resist the rotation of said brake carrying elements when the vehicle is going in the opposite direction.

4. The combination with a plurality of brakes having movable braking elements, and means for applying a brakin pressure to one of said elements, of liqui pressure operated means adapted to be actuatedby said element to cause the braking elements of the other brakes to be applied so that the resultant braking efl'fect of all of the brakes will be equalized.

5. The combination with a plurality of brakes having movable braking elements, and means for appl ing a braking pressure to all of said bra'kmg elements simultaneously, of liquid pressure operated means adapted to be actuated by one braking element for actuating the brakin elements of the other brakes so that the resu taut brakin effect of all of the brakes will be equalize 6. The combination with a plurality of brakes having rotatable drums, and brake bands engageable with said drums, of means for moving said bands into braking engagement with said drums, and liquid pres:

sure operated means adapted to be actuated by one brake band for actuating the brake bands of the other brakes so that the resulting braking1 effect of all of the brakes will be equalize 7. The combination with a plurality of brakes having rotatable drums, and brake bands engageable with said drums, of means for contractingsaid bands upon said drums and liquid pressure operated means adapted to be actuated by one brake band for actu ating the brake bands of the other brakes so that the resultant braking efiect of all of the brakes .will be equalized.

8. The combination with a plurality of brakes having rotatable drums, and brake bands engageable with said drums, of. levers pivotally connected to the ends of said brake bands, means for actuating said levers to 5 move said bands into braking enga ement with said drums, and means adapt to be actuated by one brake band for actuating the brake bands of the other brakes so that the resultant braking eflect of all of the brakes will be equalized.

9. The combination with a plurality of brakes having rotatable drums, and brake bands engageable with said drums, of liquid pressure operated means for e ualizing the resultant braking eflect of sai bands, and II actuating members connecting said brake bands to said liquid pressure operated means.

In testimony whereof, we hereunto aifix our signatures.

- SAMUEL K. WELLMAN.

. GORDON R. PENNINGTON. 

